我有一个操作列表和一个按钮。正确的链式任务取决于任务状态(已完成/出错)
当用户点击按钮时,执行的动作为,按顺序。
每次操作完成时,它会设置一个标志(更新UI),并继续执行下一个操作。
如果某个操作失败,则所有其余的操作将停止执行,并启动一个错误例程。
如果所有操作都成功,则启动成功例程。
假设:每个动作的执行需要很长的时间,并具有UI线程
上由于每个动作都在UI线程上执行的,我用任务来强制要执行短暂的延迟,以允许用户界面在继续下一个动作之前进行更新。
我设法让它工作(以某种方式)使用任务和链接在一起。
但我不确定这是否正确或最好的方法,并且如果有人可以检查我的实现,我将不胜感激?
尝试代码:
检查所有项目,并运行:所有项目应变绿,成功味精盒
取消选中一个项目,然后运行:选中的项目变为红色,错误msg框,其余动作停止运行
Xaml:
<Window x:Class="Prototype.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:cv="clr-namespace:Prototype"
Title="MainWindow" Height="450" Width="450">
<DockPanel x:Name="RootGrid" >
<!-- Run -->
<Button Content="Run"
Click="OnRun"
DockPanel.Dock="top" />
<!-- Instructions -->
<TextBlock DockPanel.Dock="Top"
Text="Uncheck to simulate failure"/>
<!-- List of actions -->
<ItemsControl ItemsSource="{Binding Actions}">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type cv:ActionVm}">
<Grid x:Name="BgGrid">
<CheckBox Content="Action"
IsChecked="{Binding IsSuccess,Mode=TwoWay}"/>
</Grid>
<DataTemplate.Triggers>
<!-- Success state -->
<DataTrigger Binding="{Binding State}"
Value="{x:Static cv:State.Success}">
<Setter TargetName="BgGrid"
Property="Background"
Value="Green" />
</DataTrigger>
<!-- Failure state -->
<DataTrigger Binding="{Binding State}"
Value="{x:Static cv:State.Failure}">
<Setter TargetName="BgGrid"
Property="Background"
Value="Red" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</DockPanel>
</Window>
代码后面:
using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using Prototype.Annotations;
namespace Prototype
{
public partial class MainWindow
{
public MainViewModel Main { get; set; }
public MainWindow()
{
// Caller injects scheduler to use when executing action
Main = new MainViewModel(TaskScheduler.FromCurrentSynchronizationContext());
InitializeComponent();
DataContext = Main;
}
// User clicks on run
private void OnRun(object sender, RoutedEventArgs e)
{
Main.RunAll();
}
}
public class MainViewModel
{
private TaskScheduler ActionScheduler { get; set; }
private TaskScheduler InternalUIScheduler { get; set; }
// List of actions
public ObservableCollection<ActionVm> Actions { get; set; }
// Constructor
// Injected Scheduler to use when executing an action
public MainViewModel(TaskScheduler actionScheduler)
{
ActionScheduler = actionScheduler;
InternalUIScheduler = TaskScheduler.FromCurrentSynchronizationContext();
Actions = new ObservableCollection<ActionVm>();
Actions.Add(new ActionVm());
Actions.Add(new ActionVm());
Actions.Add(new ActionVm()); // Mock exception.
Actions.Add(new ActionVm());
Actions.Add(new ActionVm());
}
// Runs all actions
public void RunAll()
{
// Reset state
foreach(var action in Actions) action.State = State.Normal;
// Run
RunAction();
}
// Recursively chain actions
private void RunAction(int index=0, Task task=null)
{
if (index < Actions.Count)
{
ActionVm actionVm = Actions[index];
if (task == null)
{
// No task yet. Create new.
task = NewRunActionTask(actionVm);
}
else
{
// Continue with
task = ContinueRunActionTask(task, actionVm);
}
// Setup for next action (On completed)
// Continue with a sleep on another thread (to allow the UI to update)
task.ContinueWith(
taskItem => { Thread.Sleep(10); }
, CancellationToken.None
, TaskContinuationOptions.AttachedToParent | TaskContinuationOptions.OnlyOnRanToCompletion
, TaskScheduler.Default)
.ContinueWith(
taskItem => { RunAction(index + 1, taskItem); }
, CancellationToken.None
, TaskContinuationOptions.AttachedToParent | TaskContinuationOptions.OnlyOnRanToCompletion
, TaskScheduler.Default);
// Setup for error (on faulted)
task.ContinueWith(
taskItem =>
{
if (taskItem.Exception != null)
{
var exception = taskItem.Exception.Flatten();
var msg = string.Join(Environment.NewLine, exception.InnerExceptions.Select(e => e.Message));
MessageBox.Show("Error routine: " + msg);
}
}
, CancellationToken.None
, TaskContinuationOptions.AttachedToParent | TaskContinuationOptions.OnlyOnFaulted
, InternalUIScheduler);
}
else
{
// No more actions to run
Task.Factory.StartNew(() =>
{
new TextBox(); // Mock final task on UI thread
MessageBox.Show("Success routine");
}
, CancellationToken.None
, TaskCreationOptions.AttachedToParent
, InternalUIScheduler);
}
}
// Continue task to run action
private Task ContinueRunActionTask(Task task, ActionVm action)
{
task = task.ContinueWith(
taskItem => action.Run()
, CancellationToken.None
, TaskContinuationOptions.AttachedToParent
, ActionScheduler);
return task;
}
// New task to run action
public Task NewRunActionTask(ActionVm action)
{
return Task.Factory.StartNew(
action.Run
, CancellationToken.None
, TaskCreationOptions.AttachedToParent
, ActionScheduler);
}
}
public class ActionVm:INotifyPropertyChanged
{
// Flag to mock if the action executes successfully
public bool IsSuccess
{
get { return _isSuccess; }
set { _isSuccess = value; OnPropertyChanged();}
}
// Runs the action
public void Run()
{
if (!IsSuccess)
{
// Mock failure.
// Exceptions propagated back to caller.
// Update state (view)
State = State.Failure;
throw new Exception("Action failed");
}
else
{
// Mock success
// Assumes that the action is always executed on the UI thread
new TextBox();
Thread.Sleep(1000);
// Update state (view)
State = State.Success;
}
}
private State _state;
private bool _isSuccess = true;
// View affected by this property (via triggers)
public State State
{
get { return _state; }
set { _state = value; OnPropertyChanged(); }
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public enum State
{
Normal,
Success,
Failure
}
}
[更新1]
只是为了澄清,在示例代码,ActionVm被假定为一个黑箱。它的Run()方法假定在UI线程上是一个耗时的操作,并且在完成时会自动设置其内部状态属性(视图有界)。
我可以修改/控制的唯一类是MainViewModel(运行每个任务,然后是成功/失败例程)。
如果我所做的只是一个foreach-Run(),UI将被锁定,并且没有可见的反馈,即在所有操作完成之前,操作的状态会发生更改。
因此,我试图在执行Actions之间添加一个非UI延迟,以允许视图绑定到ActionVm.State,以便在下一次阻塞运行之前至少重新绘制。
ActionVms是长时间运行的操作,将阻塞UI线程。这是正确工作所必需的。至少我试图做的是提供一些视觉反馈给用户,仍然在运行。
为什么任务*有*要在UI线程上执行?假设他们必须这样做,Application.DoEvents就是这种情况。 – usr 2014-10-06 16:00:54
这些操作涉及调用方法和访问仅在UI线程上可用的属性。 ActionVm的实际执行超出了我的控制范围。但是,我的代码和调用者之间的代码契约需要在UI线程上执行ActionVm.Run()以正确执行。 – jayars 2014-10-06 16:17:39
由于这是工作代码,因此您应该在http://codereview.stackexchange.com上找到更好的响应。 – Hogan 2014-10-06 16:35:36